The GCD of given numbers is 1.
Step 1 :
Divide $ 121 $ by $ 81 $ and get the remainder
The remainder is positive ($ 40 > 0 $), so we will continue with division.
Step 2 :
Divide $ 81 $ by $ \color{blue}{ 40 } $ and get the remainder
The remainder is still positive ($ 1 > 0 $), so we will continue with division.
Step 3 :
Divide $ 40 $ by $ \color{blue}{ 1 } $ and get the remainder
The remainder is zero => GCD is the last divisor $ \color{blue}{ \boxed { 1 }} $.
We can summarize an algorithm into a following table.
121 | : | 81 | = | 1 | remainder ( 40 ) | ||||
81 | : | 40 | = | 2 | remainder ( 1 ) | ||||
40 | : | 1 | = | 40 | remainder ( 0 ) | ||||
GCD = 1 |
This solution can be visualized using a Venn diagram.
The GCD equals the product of the numbers at the intersection.